Secondary coil

“ In this coil the 43secondary is moulded on a flexible tube, which fits loosely over the primary tube in order to compensate for changes of temperature and consequent expansions and contractions. All well-designed coils should be so arranged that the primary coil and core can be readily removed from the secondary, or vice versa. It is sometimes desirable to use a different primary. This arrangement will greatly facilitate any necessary repairs. It must be always remembered that the working of a coil depends on the insulation between primary and secondary. ”

“ The intensely disruptive power of the long spark is readily shown by its power to perforate substances, but great care must be taken that the secondary wires of a coil are led away from the body of the coil. A good plan is to hang two silk cords or stout threads from the ceiling, to which the secondary wires may be attached and kept in sight when experimenting at any distance from the coil. ”

“ When the space is filled up to the level of the paper disks and the paraffin is hard, loosen the set screw, and removing the outside disk, the coil can be slipped off, or a slight warming will loosen it. Any number of these coils can be made, and there are the advantages in this mode of construction that a bad coil will not spoil the whole secondary, and that the wire can be obtained in comparatively small quantities. ”

“ When the current is thus interrupted, the spring flies up by its elasticity and again establishes the circuit at e. This interruption was originally invented by P. Wagner. secondary coil are the Faradic or induced currents. They last only a minute fraction of a second of time. An induction coil, then, consists of a primary coil, with which a galvanic cell is connected, and a secondary coil. ”

“ The secondary windings of coils are often punctured or broken down by operating the coil with the high tension circuit open, or by trying to cause long sparks by increasing the spark gap over 3⁄8 of an inch in the open air. Coils are also broken down by allowing excessive currents to flow in the primary coil. Never cause a spark to jump over 3⁄8 of an inch.
High compression in the cylinder shortens the jumping distance of a high tension spark. ”

“ A tuner of this kind is made like an ordinary loose coupled tuning coil but it has a third coil as shown at A and B in Fig. 49. The middle coil, which is the secondary, is fixed to the base, and the large outside coil, which is the primary, is movable, that is it slides to and fro over the middle coil, while the small inside coil, which is the tickler, is also movable and can slide in or out of the middle coil. None of these coils is variable; all are wound to receive waves up to 360 meters in length when used with a variable condenser of .001 mfd. capacitance. ”

“ Four to eight large cells of dry battery are used, or eight cells Edison-Lalande—iron-clad type. Number of cells varies with size of coil needed, some classes of engines require a heavier spark than others to ignite the vapor.
When a primary and secondary are used, the primary should be made of two or three layers No. 14 B & S magnet wire, and a secondary of one pound No. 34 B & S magnet wire. There can be an independent contact breaker or the coil can be made up similar to a one-half inch spark Ruhmkorff coil (see Chapter I.) .
Fig. 12. ”

“ Thus one coil may be in
parallel with the other, and the action on the plunger will then depend
on the relative currents passing through the coils.
Coil, Choking.
A coil of high self-induction, used to resist the intensity of or
"choke" alternating currents. Any coil of insulated wire wound around
upon a laminated or divided iron core forms a choking coil. The iron
coil is usually so shaped as to afford a closed magnetic circuit.
A converter or transformer acts as a choking coil as long as its
secondary is left open. ”

“ Constructing a Coil.—Such a coil is shown in section in Fig. 89, in which the core A is a hard rubber or fiber tube, with disk ends B of the same material. The primary wire C is large in cross section, and carefully insulated. The opposite ends are brought out through the disk heads, and run to the generator, that is, the battery or dynamo. The fine wire D, which constitutes the secondary winding, is also of insulated wire, wrapped over the primary, and its ends are connected up with the sparking mechanism, as will be more fully explained hereinafter. ”

“ A primary coil of length l, having n turns, is wound upon a cylinder made of non-conducting and non-magnetic material, and upon the middle of the primary a secondary or induction coil is closely fitted. When a current of strength i is suddenly interrupted in the primary, the increment of induction through the secondary is sensibly equal to 4πin/l units. All the data required for standardizing the galvanometer can in this way be determined with accuracy. ”

“ In coils with independent circuit breakers, sliding both core and primary coil out of the secondary together or independently. (b) Moving a metal tube over or off the primary coil or core or both. Many combinations of these methods are practised. Attempts have been made to regulate battery current by rheostat,52 but it is not feasible, except in large stationary outfits. Cheap medical coils are wound with bare wire, with layers of thread between adjacent turns, or even only bedding the wire turns in paraffined paper. ”

“ The decomposition of water, which consists of oxygen and hydrogen in the formula H2O, is readily accomplished by the secondary current, and the greatest volume of gas (hydrogen) will be evolved at the negative pole. For ready reference a summary of these facts is given 45below:
Although it is customary to use bundles of fine, soft iron wire for coil cores, very excellent results have been obtained with cores made up of soft iron filings. ”

“ This cycle of operations is repeated at every revolution. If then an electrical oscillation is sent into the demagnetizing coils, and if it continues longer than one revolution of the commutator, it will demagnetize the iron core during that period of time in which the battery is disconnected and the galvanometer connected. The demagnetization of the iron which ensues produces an electromotive force in the secondary coil and causes a deflection of the galvanometer, and this deflection will continue and remain steady if the oscillation persists. ”

“ Current in the FP-QP coils is generally constant, but in the FI-QI coils is varied according to the heading and magnetic latitude of the vessel. In split-coil installations, the coil designations are often called simply the P-coil and I-coil.
Longitudinal (L) coil. Better control of the fore-and-aft components, but at greater installation expense, is provided by placing a series of vertical, athwartship coils along the length of the ship. It is the field, not the coils, which is longitudinal. Current in an L coil is varied as with the FI-QI coils. ”

“ A coil much used for electric baths has a primary winding only, regulated by the sliding in and out of the iron core, which necessitates the use of an independent vibrator, or else by varying the current strength with a rheostat. The general directions given before will answer in the present case, the only data necessary being the size of wire, which should be about six to ten layers of No. 20 B & S. The coil with movable secondaries here comes into service. Strong currents are needed for bath work, and any variety of winding can be used with this make of coil. ”

“ As the number of slots per coil-side is increased, an approach is gradually made to the case of “uniform distribution,” such as would obtain in a smooth-core armature in which the turns of the coil are wound closely side by side. Thus in the six-turn coil of fig. 12 A, which represents the development of a two-pole armature when the core is cut down to the shaft and opened out flat, there are in effect six phases compounded together, each of which differs but little from that of its next neighbour. ”

“ As before, if the additional loops are wound in continuation of the first as one coil connected to a single split-ring, this coil must be more or less concentrated into a narrow band; since if the width becomes nearly equal to or exceeds the width of the interpolar gap, the two edges of the coil-side will just as in the alternator act differentially against one another during part of each revolution. ”

“ The lighting load is entirely connected to one single phase circuit, and the motors are started and operated from this circuit with the assistance of the teazer wire. The long coil indicates the main winding of the armature, which is similar in its arrangement and size to the ordinary armature winding of a single phase alternator. The short coil which connects at one end to the middle point of the coil above mentioned, and at the other to a third collector ring is called the "teazer" coil. Its use is to generate a pressure in quadrature with that of the main coil. ”

“ These outer coils were shrunk over a hollow breech-piece of forged iron, having the fibre running lengthwise to resist the longitudinal stress. The several cylinders were shrunk over the steel inner tube or barrel. To obtain the necessary compression the exterior diameter of the inner portion is turned in a lathe slightly greater than the interior diameter of the outer coil. The outer coil is heated and expands ”

“ The coil carries an index needle moving over a scale, and there is generally an iron core in the interior of the coil but fixed and independent of it. The coil is so situated that, in its zero position when no current is passing through it, the plane of the coil is parallel to the direction of the lines of force of the field. When a current is passed through the coil it rotates in the field and displaces the index over the scale against the control of a spiral spring like the hairspring of a watch. ”

“ It requires a vastly higher voltage to make a spark jump across an air gap than it does to lead it across thus.
Fig. 116
The kind of coil we have made (only larger) is very much used in houses as a gas-lighting coil (to be described later) . It is very much used also for exploding gasolene engines. It generally passes under the name of the "make and break" coil. The revolving shaft of the engine is made to push together the ends of the wire and separate them at the right instant to make the spark for explosion. Of course this is done inside of the engine cylinder. ”

“ According to the nature of the coils armatures may be divided into the two classes of coil-wound and bar-wound. In the former class, round copper wire, double-cotton covered, is employed, and the coils are either wound by hand directly on to the armature core, or are shaped on formers prior to being inserted in the armature slots. Hand-winding is now only employed in very small bipolar machines, the process being expensive and accompanied by the disadvantage that if one section requires to be repaired, the whole armature usually has to be dismantled and re-wound. ”

“ When the large coils are divided as above described, it results that there are as many coils as there are poles, the outer loop of the small coil having a width equal to the pole-pitch, and the inner a width equal to the pole-face.
Such is the form which the “single-phase alternator” takes, but since only one-half of the armature core is now covered with winding, an entirely distinct but similar set of coils may be wound to form a second armature circuit between the coils of the first circuit. ”

“ The arrangement of the half coils, slots, and commutator segments is given in detail in Fig. 3. Each coil is reduced to one turn in the illustration, in order to simplify it. From an inspection of this diagram it may be seen that the outside end of the second coil in the upper row of figures, at the left end, is connected to the inside end of the fourth coil at segment 1, in the lower row of figures, representing the segments of the commutator. The outside end of the fourth coil is connected with the inside end of the sixth coil, at segment 2 ”

“ A piece of brass 2 in. long, 1/2 in. wide and 1/8 in. thick is used for the armature, A, to be operated by the magnet coil, C. The coil, C, is made in the usual manner by wrapping No. 14 cotton-covered magnet wire on a wooden spool that has a soft iron core. The spool is about 2-1/2 in. long. The armature, A, is drilled, making a hole just a little larger than the rod, B, and is adjusted in place by two set screws, D and E. A soft piece of iron, F, is fastened to the opposite end of the armature with a screw, which should be placed directly under the end of the coil's core. ”

“ After having been intensely heated in a furnace for ten hours, a few blows on its end from a powerful steam hammer welds its coils perpendicularly, and when a solid core has been introduced, and the mass has been well hammered on the sides, it becomes a compact cylinder of wrought iron, with the fibres all running round it. When cold it is placed in the lathe, and the muzzle end is turned down, leaving a shoulder to receive the trunnion-ring. The C coil is double, welded in a similar manner to the B coil, and it has a portion turned off, so that it may be enclosed by the trunnion-ring. ”

“ Since the field-magnet coils rotate, they must be carefully designed to withstand centrifugal force, and are best composed of flat copper strip wound on edge with thin insulation between adjacent layers. The coil is secured by the edges of the pole-shoes which overhang the pole and tightly compress the coil against the yoke-ring; the only effect from centrifugal force is then to compress still further the flat turns of copper against the pole-shoes without deformation. ”